A pickup mechanism picks up crop material, such as hay, from the ground as the agricultural machine travels across the field, which is fed into the interior of the machine, e.g. a fixed or expandable chamber in the case of a round baler, where it is rolled up to form a compact cylindrical hay package.
Round balers have become quite prevalent for their capability of producing a conveniently sized cylindrical bale, very often automatically wrapped with a sheeting material such as net or film. The round balers generally have a bale-forming chamber defined by a pair of spaced-apart side walls and a plurality of parallel belts trained around a plurality of rolls spanning between the side walls. Although in the description, the invention is explained in relation to a round baler, such a windguard mechanism may be used in combination with a pick-up for any type of agricultural machine which picks up material from the floor to be fed into the machine.
The known pickup mechanisms are usually provided with a windguard mechanism, which holds down the crop material as it is being fed to prevent it from being blown off the pickup floor and to ensure an adequate compaction of the crop material for appropriate feeding into e.g. the stuffer mechanism. The position of the windguard plate should be adjusted relatively to the pickup roll depending on the type of crop material (i.e. its structure, thickness, length, density, moisture content etc.) in order to provide optimal compression while preventing jamming of the crop material between the pickup roll and the windguard plate. When material is jammed, the machine must be halted and the jam has to be manually cleared.
US Pat. No. 6,962,041 shows a windguard for a round baler, which comprises a single floating windguard plate that pivots at the front and the middle of the tine section. When an obstruction, e.g. a stone is taken up by the pick-up and being fed with the crop into the machine, the front part of the windguard will be able to pivot upwardly. When the obstruction moves rearwardly, the back part of the windguard will also be able to pivot upwardly, while the front part of the windguard will move downwardly. Such windguard assures that the tines maintain in contact with the crop at all times as it moves over the pick-up and across the stuffer assembly, even if a possible obstruction was picked up by the pick-up. However, the windguard of U.S. Pat. No. 6,962,041 is only allowed to move upwards or downwards with relation to the pick-up and its position is only changeable when the entire structure is demounted and repositioned.
U.S. Pat. No. 6,877,304 discloses a windguard for a round baler, which comprises dual floating windguards which are able to pivot around pivot points, cfr. the windguard of U.S. Pat. No. 6,962,041, causing the tines to maintain in contact with the crop at all times. Again, if a different position of the dual floating windguards is needed due to the fact that different crop is harvested, the entire windguard will need to be disassembled and repositioned with relation to the pick-up, before taking an optimal position for the specific crops.
The U.S. Pat. No. 7,730,704 presents an agricultural press comprising a windguard, also called a material hold-down device, which comprises a plate of a specific, constant size. The entire plate or windguard is movable over a first range of movement in response to changing swath thicknesses. If a material jam arises, the entire plate can be moved over a second range of movement in order to liberate the wedged material and to overcome the jam.
The known single-plate windguard mechanisms, wherein the plate is movable with respect to the pickup wheel, have the disadvantage that when the windguard is moved away from the pickup to accommodate larger crop material, the effectiveness of the guarding function decreases. As a result, the windguard may no longer block small pieces from escaping the pickup mechanism. This is especially problematic on rocky fields, where stones may escape the pickup and may hit the back of the tractor pulling the machine, causing e.g. breaking of the tractor window and forms an actual hazard to the operator.
In turn, the dual-plate windguard mechanisms allow more freedom in adjusting a proper guarding area even for larger distances from the pickup roll, but their cost and complexity is doubled with respect to the single-plate mechanism. Moreover, crop material may be jammed between the two plates which are distant from each other and form a non-uniform and non-continuous windguard surface.